U.S. patent application number 14/108992 was filed with the patent office on 2014-04-17 for thermal interface material.
This patent application is currently assigned to HON HAI PRECISION INDUSTRY CO., LTD.. The applicant listed for this patent is HON HAI PRECISION INDUSTRY CO., LTD., Tsinghua University. Invention is credited to FENG-WEI DAI, JI-CUN WANG, YOU-SEN WANG, YUAN YAO, HUI-LING ZHANG.
Application Number | 20140102687 14/108992 |
Document ID | / |
Family ID | 43219179 |
Filed Date | 2014-04-17 |
United States Patent
Application |
20140102687 |
Kind Code |
A1 |
DAI; FENG-WEI ; et
al. |
April 17, 2014 |
THERMAL INTERFACE MATERIAL
Abstract
A thermal interface material includes a low melting point metal
matrix and a number of carbon nanotube arrays disposed in the low
melting point matrix. The low melting point metal matrix includes a
first surface and a second surface opposite to the first surface.
Each carbon nanotube array includes a number of carbon nanotubes
substantially parallel to each other. A number of first interspaces
are defined between adjacent carbon nanotube arrays. The carbon
nanotubes of the carbon nanotube arrays extend from the first
surface to the second surface.
Inventors: |
DAI; FENG-WEI; (Beijing,
CN) ; YAO; YUAN; (Beijing, CN) ; WANG;
YOU-SEN; (Beijing, CN) ; WANG; JI-CUN;
(Beijing, CN) ; ZHANG; HUI-LING; (Beijing,
CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HON HAI PRECISION INDUSTRY CO., LTD.
Tsinghua University |
New Taipei
Beijing |
|
TW
CN |
|
|
Assignee: |
HON HAI PRECISION INDUSTRY CO.,
LTD.
New Taipei
TW
Tsinghua University
Beijing
CN
|
Family ID: |
43219179 |
Appl. No.: |
14/108992 |
Filed: |
December 17, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12587637 |
Oct 8, 2009 |
8642121 |
|
|
14108992 |
|
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Current U.S.
Class: |
165/185 |
Current CPC
Class: |
H01L 23/373 20130101;
F28F 21/02 20130101; H01L 2924/00 20130101; C09K 5/12 20130101;
H01L 2924/0002 20130101; H01L 2924/0002 20130101 |
Class at
Publication: |
165/185 |
International
Class: |
F28F 21/02 20060101
F28F021/02 |
Foreign Application Data
Date |
Code |
Application Number |
May 27, 2009 |
CN |
2009101077404 |
Claims
1. A thermal interface material, comprising: a low melting point
metal matrix comprising a first surface and a second surface
opposite to the first surface; a plurality of carbon nanotube
arrays disposed in the low melting point metal matrix, each carbon
nanotube array comprising a plurality of carbon nanotubes
substantially parallel to each other; and a plurality of first
interspaces defined between adjacent carbon nanotube arrays,
wherein the plurality of carbon nanotubes of the plurality of
carbon nanotube arrays extend from the first surface to the second
surface.
2. The thermal interface material as claimed in claim 1, wherein
each of the plurality of first interspaces is sized in a range from
about 10 microns to about 500 microns.
3. The thermal interface material as claimed in claim 2, wherein a
plurality of second interspaces is defined between adjacent carbon
nanotubes of each of the plurality of carbon nanotube arrays.
4. The thermal interface material as claimed in claim 3, wherein
each of the plurality of second interspaces is sized in a range
from about 20 nanometers to about 500 nanometers.
5. The thermal interface material as claimed in claim 4, wherein
the material of the low melting point metal matrix is filled in the
plurality of second interspaces and the plurality of first
interspaces.
6. The thermal interface material as claimed in claim 1, wherein
one portion of the plurality of carbon nanotubes is exposed out of
the low melting point metal matrix from the first surface.
7. The thermal interface material as claimed in claim 1, wherein
the low melting point metal matrix is made of indium (In), gallium
(Ga), an alloy of antimony (Sb) and bismuth (Bi), an alloy of lead
and tin, or any combination thereof.
8. The thermal interface material as claimed in claim 1, wherein
the melting point of the low melting point metal matrix is below
200.degree. C.
9. The thermal interface material as claimed in claim 1, wherein
the thickness of the low melting point metal matrix is in a range
from about 10 micros to about 1 millimeter.
10. A thermal interface material, comprising: a plurality of carbon
nanotube arrays spaced with each other, wherein each of the
plurality of carbon nanotube arrays comprises a plurality of carbon
nanotubes parallel to each other and extending from a same
direction, each of a plurality of first interspaces is defined
between two adjacent carbon nanotube arrays, and each of a
plurality of second interspaces is defined between two adjacent
carbon nanotubes of each of the plurality of carbon nanotube
arrays; and a low melting point metal material filled in the
plurality of first interspaces and the plurality of second
interspaces to form a low melting point metal matrix.
11. The thermal interface material as claimed in claim 10, wherein
one portion of the plurality of carbon nanotubes is exposed out of
the low melting point metal matrix.
12. The thermal interface material as claimed in claim 10, wherein
each of the plurality of first interspaces is sized in a range from
about 10 microns to about 500 microns.
13. The thermal interface material as claimed in claim 10, wherein
each of the plurality of second interspaces is sized in a range
from about 20 nanometers to about 500 nanometers.
14. The thermal interface material as claimed in claim 1, wherein
the low melting point metal material is indium (In), gallium (Ga),
an alloy of antimony (Sb) and bismuth (Bi), an alloy of lead and
tin, or any combination thereof.
15. The thermal interface material as claimed in claim 10, wherein
the melting point of the low melting point metal material is below
200.degree. C.
16. The thermal interface material as claimed in claim 10, wherein
the thickness of the low melting point metal matrix is in a range
from about 10 micros to about 1 millimeter.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 12/587,637 filed on Oct. 08, 2009 entitled,
"THERMAL INTERFACE MATERIAL HAVING A PATTERNED CARBON NANOTUBE
ARRAY AND METHOD FOR MAKING THE SAME". The disclosures of the
above-identified applications are incorporated herein by
reference.
BACKGROUND
[0002] 1. Technical Field
[0003] The present disclosure relates to a thermal interface
material and a method for fabricating the same, and particularly to
a thermal interface material having a patterned carbon nanotube
array and a method for fabricating the same.
[0004] 2. Description of Related Art
[0005] Many electronic components such as semiconductor chips are
becoming progressively smaller with each new product release, while
at the same time the heat dissipation requirements of these kinds
of components are increasing due to their improved ability to
provide more functionality. Commonly, a thermal interface material
is utilized between an electronic component and a heat sink in
order to fill air spaces therebetween and thereby promote efficient
heat transfer.
[0006] Carbon nanotubes (CNTs) produced by means of arc discharge
between graphite rods were first discovered and reported in an
article by Sumio Iijima, entitled "Helical Microtubules of
Graphitic Carbon" (Nature, Vol. 354, Nov. 7, 1991, pp. 56-58). An
another article authored by Savas Berber, entitled "Unusually High
Thermal Conductivity of Carbon Nanotubes" (page 4613, Vol. 84,
Physical Review Letters 2000) discloses that a heat conduction
coefficient of a carbon nanotube can be 6600 W/mK
(watts/milliKelvin) at room temperature. That tends to make CNTs
ideal candidates for thermal interface material.
[0007] A method for making the thermal interface material having a
CNT array is by diffusing particles with a high heat conduction
coefficient therein. The particles can be made of graphite, boron
nitride, silicon oxide, alumina, silver, or other metals. However,
the diffusing particles can not be uniformly dispersed into the CNT
array, because the interspaces therein is small, and interfaces
between some diffusing particles and CNTs in the CNT array is high.
Therefore, the heat conduction coefficient of the thermal interface
material is low and cannot adequately meet the heat dissipation
requirements of modern electronic components.
[0008] Another method for making the thermal interface material
having a CNT array is by injection molding. In this method, the CNT
array is filled with a polymer material. However, the thermal
interface material formed by injection molding is relatively thick.
This increases a bulk of the thermal interface material, reduces
its flexibility. Furthermore, because of the polymer material, the
heat conducting efficiency of thermal interface material is
low.
[0009] Therefore, a simple method for making a thermal interface
material is desired, which is thin, and has a high heat conducting
efficiency.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Many aspects of the embodiments can be better understood
with references to the following drawings. The components in the
drawings are not necessarily drawn to scale, the emphasis instead
being placed upon clearly illustrating the principles of the
embodiments.
[0011] FIGS. 1A though 1E are sectional views of one embodiment of
a method for making a thermal interface material.
[0012] FIGS. 2A through 2C are sectional views of one embodiment of
a method for making a pattered carbon nanotube array used in the
method for making the thermal interface material in FIGS. 1A
through 1E.
[0013] FIG. 3 is an enlarged view of part III in FIG. 2C.
[0014] FIG. 4 shows a Scanning Electron Microscope image of the
patterned carbon nanotube array in FIG. 2C.
[0015] FIG. 5 is a schematic, enlarged view of one embodiment of a
container used in the method of FIG. 1B.
[0016] FIG. 6 is a schematic view of one embodiment of a thermal
interface material having a patterned carbon nanotube array.
[0017] FIG. 7 is an enlarged view of part VII in FIG. 6.
DETAILED DESCRIPTION
[0018] Referring to FIGS. 1A through 1E, one embodiment of a method
for making a thermal interface material 100 having a patterned CNT
array 14 is illustrated. The method includes the following steps:
[0019] (a) providing a patterned CNT array 14 on a substrate 10,
the patterned CNT array 14 including a plurality of CNT arrays 142
and a plurality of first interspaces 144 defined between two
adjacent CNT arrays 142; [0020] (b) providing a container 20 and
disposing the substrate 10 with the CNT arrays 142 into the
container 20; [0021] (c) providing a plurality of low melting point
metallic nanoparticles 300 and filling the first interspaces 144
with the low melting point metallic nanoparticles 300; [0022] (d)
heating the low melting point metallic nanoparticles 300 in the
container 20 to a liquid state, then combining them with the CNT
arrays 142 to form a composite material 80 on the substrate 10;
[0023] (e) peeling off the composite material 80 from the substrate
10, and obtaining a thermal interface material 100.
[0024] Referring to FIGS. 2A through 2C, in step (a), the patterned
CNT array 14 can be formed by the substeps of: [0025] (a1)
providing a substantially flat and smooth substrate 10; [0026] (a2)
forming a patterned catalyst layer 12 on the substrate 10, wherein
the patterned catalyst layer 12 includes a plurality of catalyst
sections 122 with an interval 124 formed between two adjacent
catalyst sections 122; [0027] (a3) annealing the substrate 10 with
the patterned catalyst layer 12 at a temperature in a range from
about 700.degree. C. to about 900.degree. C. in air for about 30
minutes to about 90 minutes; [0028] (a4) heating the substrate 10
with the patterned catalyst layer 12 at a temperature in the
approximate range from about 500.degree. C. to about 740.degree. C.
in a furnace with a protective gas therein; and [0029] (a5)
supplying a carbon source gas in the furnace for about 5 minutes to
about 30 minutes and growing the patterned CNT array 14 from the
catalyst sections 122 on the substrate 10.
[0030] In step (a1), the substrate 10 can be a P-type silicon
wafer, an N-type silicon wafer, or a silicon wafer with a film of
silicon dioxide thereon. In one embodiment, a 4-inch P-type silicon
wafer is used as the substrate 10.
[0031] In step (a2), the catalyst of the patterned catalyst layer
12 can be made of iron (Fe), cobalt (Co), nickel (Ni), or any alloy
thereof. The intervals 124 correspond to the first interspaces 144.
Widths of the intervals 124 are in a range from about 10 microns to
about 500 microns.
[0032] In one embodiment, the whole substrate 10 is patterned with
Fe films 5 nanometers (nm) thick formed by electron beam
evaporation through shadow masks, containing squared openings with
side lengths of about 10 to about 250 millimeters (mm) at pitch
distances of about 50 mm to about 200 mm. Therefore, the patterned
catalyst layer 12 including a plurality of the catalyst sections
122 and a plurality of the intervals 124, is formed on the
substrate 10.
[0033] In step (a4), the protective gas can be made up of at least
one of nitrogen (N.sub.2), ammonia (NH.sub.3), and a noble gas. In
step (a5), the carbon source gas can be a hydrocarbon gas, such as
ethylene (C.sub.2H.sub.4), methane (CH.sub.4), acetylene
(C.sub.2H.sub.2), ethane (C.sub.2H.sub.6), or any combination
thereof.
[0034] In step (a5), a CNT array 142 can be grown upon each
catalyst section 122, therefore the patterned CNT array 14
including a plurality of the CNT arrays 142 can be achieved on the
substrate 10. The plurality of first interspaces 144 is defined
between two adjacent CNT arrays 142. Widths of the first
interspaces 144 are in a range from about 10 microns to about 500
microns.
[0035] Referring to FIG. 2C, FIG. 3 and FIG. 4, each CNT array 142
can be about 10 microns to about 1 millimeter high and include a
plurality of carbon nanotubes substantially parallel to each other
and substantially perpendicular to the substrate 10. The CNT arrays
142 are essentially free of impurities, such as carbonaceous or
residual catalyst particles. A plurality of second interspaces 146
is defined between the adjacent carbon nanotubes in each CNT array
142. Widths of the second interspaces 146 are in a range from about
20 nm to about 500 nm.
[0036] It is to be understood that the area of the patterned CNT
array 14 is in accordance with the area of the substrate 10. Thus,
the area of the patterned CNT array 14 can be controlled by
adjusting the area of the substrate 10.
[0037] In step (b), the container 20 can be made up of rigid
materials with high melting points, such as metal or glass.
Referring to FIG. 5, the container 20 includes a first board 21, a
second board 22, a third board 23, a fourth board 24, and a basic
board 25. The first board 21 is facing and substantially parallel
to the third board 23. The second board 22 is facing and
substantially parallel to the fourth board 24. The first board 21,
the second board 22, the third board 23, and the fourth board 24
are substantially perpendicular to the basic board 25. The first
board 21, the second board 22, the third board 23, the fourth board
24, and the basic board 25 together define a space 208.
[0038] In step (b), before disposing the substrate 10 into the
container 20, a graphite paper 206 can be disposed in the space 208
of the container 20. In one embodiment, a graphite paper 206 (shown
in FIG. 1B and FIG. 1C) is disposed in the space 208, then the
substrate 10 with the patterned CNT array 14 is disposed on the
graphite paper 206 above the basic board 25.
[0039] In step (c), the material of the low melting point metallic
nanoparticles 300 can be indium (In), gallium (Ga), an alloy of
antimony (Sb) and bismuth (Bi), an alloy of lead and tin, or any
combination thereof. The melting point of the low melting point
metallic nanoparticles 300 is below 200.degree. C. The size of the
low melting point metallic nanoparticles 300 is in a range from
about 10 nanometers to about 2500 nanometers. The first interspaces
144 can be filled up to a level not above free ends of the carbon
nanotubes of the CNT arrays 142 with the low melting point metallic
nanoparticles 300.
[0040] Step (d) includes the following substeps of: [0041] (d1)
placing the container 20 having the CNT arrays 142 into a chamber,
wherein the chamber is at 20-200.degree. C. and filled with at
least one inert gas; [0042] (d2) increasing the temperature of the
chamber at a rate of about 5.degree. C. per minute, until the
temperature of the chamber is about 150.degree. C. to about
200.degree. C.; and [0043] (d3) holding the temperature from about
0.2 hours to about 1.5 hours, and melting the low melting point
metallic nanoparticles 300 to a liquid state; [0044] (d4) cooling
the chamber to room temperature in an environment of inert gas,
holding the room temperature (about 25.degree. C.) for a while
until the low melting point metallic nanoparticles 300 in the
liquid state are solidified to a solid state low melting point
metal matrix 30, and combined with the patterned CNT array 14 to
form the composite material 80.
[0045] In step (d3), the liquid state low melting point metal can
be dispersed in the first interspaces 144 and the second
interspaces 146. The low melting point metallic nanoparticles 300
in a liquid state flow into the second interspaces 146 and the
first interspaces 144 simultaneously, or from the first interspaces
144 into the second interspaces 146.
[0046] In step (d4), a thickness of the solid low melting point
metal matrix 30 can be controlled by adjusting the quantity of the
low melting point metallic nanoparticles 300. In one embodiment,
the thickness of the solid melting point metal matrix 30 can be a
less than the height of the carbon nanotubes of the patterned CNT
array 14. Therefore one portion of the carbon nanotubes of the
patterned CNT array 14 is exposed from the composite material
80.
[0047] In step (e), the composite material 80 includes the low
melting point metal matrix 30 and the patterned CNT array 14. The
low melting point metal matrix 30 is dispersed in the first
interspaces 144. The low point metal matrix 30 is combined with the
patterned CNT array 14 to form the composite material 80. The
composite material 80 can be peeled off from the substrate 10. In
one embodiment, a portion of the composite material 80 is peeled
off from the substrate using a knife, thereby a thermal interface
material 100 is gained.
[0048] Referring to FIG. 6, one embodiment of a thermal interface
material 100, formed by the method described above, includes a low
melting point metal matrix 30 and a patterned CNT array 14. The
patterned CNT array 14 includes a plurality of CNT arrays 142 and a
plurality of first interspaces 144. The patterned CNT array 14 is
dispersed in the low melting point metal matrix 30. The first
interspaces 144 are filled with the low melting point metal matrix
30.
[0049] Each CNT array 142 includes a plurality of carbon nanotubes
substantially parallel to each other and substantially
perpendicular to the substrate 30. The CNT arrays 142 can have a
height of about 10 microns to about 1 millimeter. The first
interspaces 144 are defined between the adjacent CNT arrays 142.
Widths of the first interspaces 144 are in a range from about 10
microns to about 1 millimeter.
[0050] Referring to FIG. 7, the second interspaces 146 are defined
between adjacent carbon nanotubes in each CNT array 142. The low
melting point metal matrix 30 is also filled in the second
interspaces 146. Widths of the second interspaces 142 are in a
range from about 20 nm to about 500 nm.
[0051] The low point metal matrix 30 can be made of indium (In),
gallium (Ga), an alloy of antimony (Sb) and bismuth (Bi), an alloy
of lead and tin, or any combination thereof. A thickness of the low
melting point metal matrix 30 can be in a range from about 10
microns to 1 about millimeter.
[0052] It may be understood that the thickness of the low melting
point metal matrix 30 can be less or greater than the height of the
carbon nanotubes of the patterned CNT array 14. In one embodiment,
the thickness of the low melting point metal matrix 30 is less than
the height of the carbon nanotubes of the patterned CNT array 14.
Therefore, ends of the carbon nanotubes are exposed out of the
thermal interface material 100. This ensures that the carbon
nanotubes in the thermal interface material 100 thermally contact
an electronic element and a heat sink directly.
[0053] In use, the thermal interface material 100 of the present
embodiment can be disposed between an electronic component and a
heat spreader. When ambient temperature is above the melting point
of the thermal interface material 100, the low melting point
metallic matrix 30 changes to a liquid capable of filling the gaps
between the electronic component and the heat spreader, and as
such, reduces the thermal contact resistance therebetween. The
patterned CNT array 14 includes a plurality of first interspaces
144, the low melting point metal matrix 30 is uniformly filled in
the first interspaces 144, and the thermal interface material 100
has a higher thermal conductivity. Further, the method for
fabricating the thermal interface material 100 is simple and can be
applied in mass production at a low cost.
[0054] It is also to be understood that the above description and
the claims drawn to a method may include some indication in
reference to certain steps. However, the indication used is only to
be viewed for identification purposes and not as a suggestion as to
an order for the steps.
[0055] Finally, it is to be understood that the above-described
embodiments are intended to illustrate rather than limit the
disclosure. Variations may be made to the embodiments without
departing from the spirit of the disclosure as claimed. The
above-described embodiments illustrate the scope of the disclosure
but do not restrict the scope of the disclosure
* * * * *